Screw presses



Nov. 17, 1959 E. v. JUNG 2,912,923

SCREW PRESSES Filed March 12, 195e g :i I .51 l l v 2/ |5 I I I n 5 I I 52 I .l S3 l l l g 54' 4 i 22 i 19 Jan/WM5@ a/rw( 22% vor United States Patent() M tiebolaget Landsverk, Landskrona, Swedena company of Sweden ApplicaaunMarch E1 2, 195s, serial No. 721,018

z claims. (c1. o-'117) For removal of liquid from materials such-as sulphite pulp, beet pulp and fish meal pulp presses of different 4kinds have been used, such as screw presses with vertical shaft. These presses comprise a spindle with screw blades surrounded by a perforated drainage jacket at a distance from `,the .spindle` which decreases downwards in kthe feed direction. .The-spindle has been rotated by means of a driving device which together with a bearing for the spindle has been located at the upper end of the shaft of the spindle, where it is out of the way for the discharge of the material at the lower end of the press. The press material is usually fed from the side to the upper end of the screw blades.

The invention is based on the realization that in the known presses a sufficient capacity cannot be obtained, and that the final pressure at the discharge end cannot be increased to such a value, that a suflicient degree of dryness is attained. The main reason hereof has been found to be that the ratio of the obtained and the theoretically possible feeding through a horizontal plane at the level of the upper ends of the screw blades has been insufficient. The material at the upper end of the screw has too much rotated with the screw, and the actual ratio of compression at the supply end as a function of the angle of rotation of the screw is therefore essentially less than the geometrical ratio corresponding to only axial displacement of the material.

It is an object of the invention to remove these disadvantages and to provide such a performance of the press that the feeding capacity and thereby the capacity of the press and the final pressure at the discharge end is considerably improved.

It has now been found that an essential improvement is obtained, if a central hopper for the material to be pressed is provided above the portion of the spindle carrying the'screw blades and has a sufficient height to cause the material collected therein to exert a static pressure upon the layer of material at the level of the upper end of said portion of the spindle. This hopper, however, prevents the ordinary use of the driving gear on the upper end of the screw, and according to the invention the driving gear, therefore, is mounted on the lower end of the spindle beneath a number of discharge openings.

In the boundary layer between the hopper and the press chamber a friction will arise between the material which tends to rotate with the screw and the material in the hopper, and the friction resistance counteracting the rotation of the material caught by the upper screw blades will be proportional to the static pressure and thus increase with the height of the material stored in the hopper. At the same time the weight of the material in the hopper will press material axially downwards at the level, where it is grasped by the upper screw blades. 'By simple means it is thus possible to obtain an effective feeding of the material into the screw, and a further advantage is that this material is already somewhat pre- .i 2,912,923 Patented N0v- 117 11959 2 l, compressed. This fact .has proved to be of the greatest importance in order vto attain .a high .pressure at the dise charge end and thereby aneifective. forcing of liquid out of the material and a corresponding degree ofv dryness.

The invention is moreclearly disclosed hereinafter in connection with the accompanying drawing showing a vertical sectional view of'a .press according to oneform of the invention. v

A central and downwardly widened body or spindle 1 is provided with four pairs of separate screw blades S1, S2, S3, and 184,' which are closely surrounded by a stationary and cylindricalperforated.drainage jacket 3within an outer concentric cylinder or. casing 2,. Between the spindle and the jacket a number of press chambers are formed, from which the liquid forcedout of the -maf terial passes through the` jacket to the spacebetween .the two cylindersand flows olf through the outlet 4.

Between the proximate press chambers and pairs of screw blades rows of resistors in'theform of short guide plates 5Y are providedand removably secured to the outer cylinder 2. Theshaft of4 the spindle hasfits upper end mounted in a bearing 6, which is supported by arms 8 removably fastened to the outer cylinder 2 and covered by a conical cap 7.

To the upper end of the cylinder 2 a central hopper 9 is connected, which has a conical and downwards somewhat widened wall 10 with the same diameter at its lower end as the drainage jacket 3. The hopper has an upper narrowing portion 11 connected with a supply channel 12 with a feed screw 13.

The lower end of the shaft is carried by a thrust bearing 14 mounted in the upper wall of a housing 15, which serves as a base plate for the press, and within the housing the shaft is provided with a gear wheel 16 engaging a driving wheel 17 such as a worm wheel on a motor 18 mounted on the housing 15.

The two cylinders 2, 3 are at their lower end connected by an end ring 19 resting on a supporting ring 20, and between these rings a rotatable valve disk 21 is mounted. The ring 20 and the disk 21 are provided with corresponding openings, and if the disk is displaced relative to the ring 20 the free openings in the ring may be reduced for regulating the discharge and the pressure. Below the valve device a collecting room 25 for the discharged material is formed by a ring-shaped bottorn 24 secured to the shaft and a stationary cylindrical wall 23, and the collected material may be removed through an opening in the wall by means of a stationary scraper or the like.

The pulp is fed by the feed worm 13 or a pump to the hopper 9, from which it enters the press chamber between the drainage jacket 3 and the spindle 1. In

case of uneven supply of material the hopper serves as a compensating container and should have a correspondingly great volume. When pressing beet pulp it has thus been found suitable to give the hopper a volume sufiicient for full feeding of the press chamber during at least 7 minutes. During normal operation, however, the height of material in the hopper should preferably not pass below 1.5 meters corresponding to an overpressure of 0.15 atm. at the upper ends of the screw blades. As the hopper is located centrally above the spindle and the gear is provided at the lower end thereof, whereby the material has a substantially free passage through the hopper, the static pressure of the material is effectively utilized. The ratio of the attained and the theoretically creased final pressure at a certain ratio of the pitch of the screw blades at the charge and the discharge ends.

' the spindle and theijacketinto a plurality of press cham- When the material is caught by the screw blades it is forced downwards alongl a somewhat helical path and against the drainage jacket 3, through whichthe liquid passes, and to prevent the material from rotating with the screw as a unit the resistors 5 are provided between the screw blades S1, S2, S3, and S4. The arms 8 above the screw blades are also formed so as to guide the material and counteract rotation.

It is obvious that the press as shown may be modiled in different Ways within the scope of the invention. Thus the spindle may also be perforated and be used for drainage. It is also possible to close the upper portion of the hopper and to feed the material by the worm 13 under pressure into the hopper in which case the height thereof may be reduced. 1

What I claim is:

1. In a screw press, a vertical rotatable screw comprising a spindle with downwardly increasing diameter and provided with outwardly extending screw blades, said spindle having an upper and a lower shaft end, a stationary perforated drainage jacket surrounding said screw, a casing surrounding said jacket, a plurality of resistors secured to said casing and extending inward between bers with downwardly decreasing volume, a central hopper located above the upper shaft end and having a height larger than its Width, a feeding device located above the hopper, a bearing for the upper shaft end located at the bottom of the hopper, a plurality of discharge openings distributed around the lower portion of the screw, a common valve member for varying the passages through said discharge openings, a thrust bearing Vfor the lower shaft end provided in a base plate, and a drive gear on the lower shaft end located below said thrust bearing.

2. A screw press as claimed in claim `l, wherein the drive gear is located within a gear box forming the base plate of the screw press.

References Cited in the tile of this patent UNITED STATES PATENTS 

